Since the advent of the use of pneumatic tires on motor vehicles numerous attempts have been made to provide a tire that could be driven a distance safely after damage occurs causing partial or complete deflation.
The patent literature is replete with solutions to the problem although up to now no completely satisfactory solution has been realized.
Broadly speaking, the solutions, which have been presented, fall into three categories: (1) the tire and wheel are removed and replaced, (2) only the tire is removed and replaced, or (3) the tire is temporarily replaced or repaired in situ.
Some solutions which have been proposed in the third category are to: (1) provide a secondary wheel which is automatically brought into use upon deflation, (2) use a tire having multiple separate compartments so that complete deflation does not occur, (3) use a tire capable of self-healing the damage, (4) provide a means of reinflating the tire, or (5) provide a supportive insert within the tire.
An early example of the insert approach is the utilization of a portion of the metal rim as the insert. This idea is disclosed in the patent to Omeron, U.S. Pat. No. 2,844,180. Unfortunately, the frictional action between the metal insert and the tire casing causes abrasion and excessive temperature rise which soon destroys the casing even at very low travel velocity. Use of a lubricant in the contact area between the insert and the casing for minimizing this functional damage has been proposed as a remedy in the patent to F. S. Dickenson, U.S. Pat. No. 2,040,645. At best this is only a stop gap and could not extend the life of the tire any appreciable time.
An early example of a cushion type insert is disclosed in the patent to J. E. Lydone, U.S. Pat. No. 2,708,469. In effect, this device has the wall of the casing in the tread area considerably thickened. Upon deflation the tire would assume the position at the ground contact level as illustrated in FIG. 1 on the right hand side of the patent drawing. This type of tire would give an extremely inferior ride to that of the standard tire when fully inflated. The patent to Rosenbaum, U.S. Pat. No. 3,049,162 illustrates the use of a ring of plastic material attached to the rim and extending into the cavity defined by the casing. In order to provide free rotation of the ring on the rim, bearings are provided in a variation of the assembly. This is a very expensive, complex device for the required use. Another example of a cushion support attached to the rim is disclosed in the patent to Powers, U.S. Pat. No. 3,392,772.
The patent to Wynbelt, U.S. Pat. No. 3,578,056 discloses a tubular, toroidal insert used as a cushion. The insert is immovably wedged against the inner surface of the casing and is hollow. A flexible tube through the insert allows the tire to be completely inflated and pressure adjustments to be made.
Although probably not legitimately classifiable as inserts the group of patents which disclose the idea of completely filling the tire cavity with, for example, hollow rubber balls as disclosed in U.S. Ser. No. 799,859 or with foam filler as disclosed in U.S. Pat. No. 3,381,735, is of interest in the category.